1. Field of the Invention
The present invention generally relates to a device which allows a single telephone line to be used for both facsimile and voice communications and, more particularly, to a device which automatically determine whether a facsimile transmission is being sent to the user's telephone station and, if not, allows the telephone call through to the user's telephone handset.
2. Description of the Prior Art
Facsimile equipment allows textual and graphical image data to be transmitted between users via telephone lines. Many users find the instantaneous transfer of data afforded by facsimile equipment preferable to overnight delivery mail services. A small firm may have a dedicated telephone line which handles facsimile transmissions as well as a telephone line used for business conversations; however, having an extra dedicated telephone line requires paying an additional monthly telephone service charge for that line. In the long term, the telephone service charges can be quiet expensive by comparison to the amount of facsimile transmissions the user sends or receives.
Small firms may prefer to use the same telephone line for both facsimile transmissions and business conversations. One problem encountered with using the same telephone line is that if the facsimile is set up to receive transmissions, business callers will not be able to get through to the user since the facsimile machine will answer the call expecting a facsimile transmission. Likewise, if the user decides to receive business calls, every time a facsimile transmission comes in, the user will hear a loud tone from the caller's facsimile machine and will be required to switch his facsimile machine on. Using a single line in the above-described fashion is not very satisfying since the small firm risks losing business callers and at the same time is not providing an efficient facsimile reception station.
U.S. Pat. No. 4,677,660 to Yoshida discloses a communication apparats which selectively allows voice communication or image communication on the same telephone line. In operation, an operator can send facsimile transmissions automatically or can dial numbers for voice communication by depressing a button on the phone. In the reception mode, a call is detected by a detector circuit. A CED signal (a called station identifying signal indicating that the called station is a non-voice communication terminal) is transmitted to the calling party when a ring is detected and a group identifying signal such as GI2 (for G2 facsimile equipment) or DIS (for G3 facsimile equipment) is transmitted to the calling party every three seconds for a period of twenty seconds. If the calling party is operating facsimile equipment, a GC2 or DCS signal will be sent in response to the group identifying signal and will establish communications between the two facsimile machines such that image data can automatically be received. If the calling party does not respond within the time period in which the group identifying signal is sent, it is assumed that the calling party is operating a voice communication terminal and an operator calling circuit is activated. The operator will then depress a button on the phone and can engage in a conversation with the calling party.
One problem with the Yoshida device is that it is not as automatic as one would like. A caller will be subjected to waiting up to twenty seconds before the Yoshida device decides that the calling party desires voice communication rather than facsimile communication. During this time interval, many callers may assume something is wrong with the operator's receiving station and simply hang up.
U.S. Pat. No. 4,584,434 to Hashimoto shows an automatic information reception terminal which receives voice and image information. In operation, a ringing signal from an incoming call is detected and an outgoing message is sent to the calling party. The calling party can leave his name or other information on a tape recording device and can remotely command the facsimile to receive information. When a remote command signal is issued by the caller pushing a button on his phone, a ringing signal generator is activated. The ringing signal generator produces telephone ring signal which is sensed by a ring signal detector that activates the facsimile for reception.
The Hashimoto device requires a remote control signal from the caller and a remote circuit must request a reset of the terminal. Therefore, the Hashimoto device is not fully automatic.